Internet protocol (IP) multimedia subsystem (IMS) is defined by the Third Generation Partnership Project (3GPP) as a new mobile network infrastructure that enables the convergence of data, speech, and mobile network technology over an IP-based infrastructure. IMS bridges the gap between the existing traditional telecommunications technology and Internet technology, allowing network operators to offer a standardized, reusable platform with new, innovative services by enhancing real time, multimedia mobile services, such as voice services, video telephony, messaging, conferencing, and push services. IMS can be used to provide services for both mobile networks and fixed networks at the same time, providing unique mixtures of services with transparency to the end-user.
IMS supports the establishment of any type of media session (e.g., voice, video, text, etc.) and provides the service creator the ability to combine services in the same session and dynamically modify sessions “on the fly” (e.g., adding a video component to an existing voice session). As a result, new and innovative user-to-user and multi-user services become available, such as enhanced voice services, video telephony, chat, push-to-talk, and multimedia conferencing, all of which are based on the concept of a multimedia session. The underlying IMS infrastructure enables mobile IP communication services via its ability to find a user in the network and then to establish a session with the user. The key IMS components enabling mobility management are the call session control function (CSCF) and home subscriber server (HSS). The CSCF is essentially a proxy, which aids in the setup and management of sessions and forwards messages between IMS networks. The HSS holds all of the key subscriber information and enables users (or servers) to find and communicate with other end users.
FIG. 1 is a block diagram illustrating access in an IMS system. In FIG. 1, a visited network 100 includes a proxy CSCF (P-CSCF) 102. The visited network 100 may be part of or in communication with a mobile or fixed network. Accordingly, visited network 100 includes a gateway general packet radio service (GPRS) support node (GGSN) 104, which may in turn communicate with a serving GPRS support node (SGSN) 106 that is in communication with a radio access network (RAN) 108 in which an IMS subscriber is currently located. The subscriber's home network 110 includes an HSS 112 with the subscriber's profile, an interrogating CSCF (I-CSCF) 114, and a serving CSCF (S-CSCF) 116.
IMS uses session initiation protocol (SIP) for multimedia session negotiation and session management. For example, SIP REGISTER and INVITE messages are used in communication with P-CSCF 102, I-CSCF 114, and S-CSCF 116 in FIG. 1. The IMS is essentially a mobile SIP network designed to support this functionality, providing routing, network location, and addressing functionalities. The DIAMETER protocol is used between I-CSCF 114 and HSS 112 and between S-CSCF 116 and HSS 112. DIAMETER provides an authentication, authorization and accounting (AAA) framework for applications such as network access or IP mobility in both local and roaming situations.
P-CSCF 102 is the first contact point within the IMS and behaves like a proxy. The P-CSCF 102 forwards the SIP REGISTER request received from the subscriber's user equipment (UE) (not shown) via GGSN 104, SGSN 106, and RAN 108 to l-CSCF 114, whose identity is determined using the home domain name, as provided by the UE. The SIP messages are forwarded to S-CSCF 116, whose identity P-CSCF 102 received as a result of the registration procedure. P-CSCF 102 also forwards SIP requests or responses to the UE, generates call detail records (CDRs), maintains a security association between itself and each UE, performs SIP message compression and decompression, and authorizes bearer resources and QoS management.
I-CSCF 114 is the contact point within the subscriber's home network 110 for all connections destined to the subscriber or for a roaming subscriber currently located within that network operator's service area. The I-CSCF 114 assigns S-CSCF 116 to a user performing SIP registration, routes a SIP request received from another network towards S-CSCF 116, obtains the address of S-CSCF 116 from HSS 112 and forwards the SIP request or response to the S-CSCF 116.
S-CSCF 116 performs the session control services for the UE and maintains session state as needed by the network operator for support of the services. S-CSCF 116 accepts registration requests, makes its information available through HSS 112, and provides session control. S-CSCF 116 also acts as a proxy server, i.e., it accepts requests and services them internally or forwards them on, and behaves as a User Agent, i.e., it terminates and independently generates SIP transactions. S-CSCF 116 is responsible for interaction with services platforms for the support of services on behalf of an originating endpoint.
HSS 112 holds the subscriber profile and keeps track of the core network node that is currently holding the subscriber. HSS 112 provides mobility management, call and/or session establishment support, and supports the call and/or session establishment procedures in IMS. HSS 112 supports user security information generation, authentication procedures, user identification handling, access authorization, service authorization support service provisioning support, and provides support for application services. HSS 112 may also communicate with an application server (not shown) to offer value added services. The application server and can reside either in the user's home network or in a third party location and enables different services in the IMS network like call-forwarding, call waiting, presence & instant messaging. The application server communicates with the HSS using the DIAMETER protocol.
IMS network operators adopting an IMS infrastructure early stand to gain sizeable competitive advantages. Despite those benefits, it is still desirable to evolve network infrastructure incrementally rather than make radical changes. Accordingly, network operators must provide support for other legacy networks while implementing an IMS infrastructure. A need therefore exists for supporting database access in internet protocol multimedia subsystem network environment while supporting legacy network subscriber database access.